From: Yu Zhao <yuzhao@google.com>
Date: Fri, 16 Jun 2017 21:02:31 +0000 (-0700)
Subject: swap: cond_resched in swap_cgroup_prepare()
X-Git-Tag: release-20171130_firefly~4^2~100^2~1^2~1^2~36
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=6af90091b61050c022c952696180c5adda217e7c;p=firefly-linux-kernel-4.4.55.git

swap: cond_resched in swap_cgroup_prepare()

commit ef70762948dde012146926720b70e79736336764 upstream.

I saw need_resched() warnings when swapping on large swapfile (TBs)
because continuously allocating many pages in swap_cgroup_prepare() took
too long.

We already cond_resched when freeing page in swap_cgroup_swapoff().  Do
the same for the page allocation.

Link: http://lkml.kernel.org/r/20170604200109.17606-1-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/mm/swap_cgroup.c b/mm/swap_cgroup.c
index b5f7f24b8dd1..40dd0f9b00d6 100644
--- a/mm/swap_cgroup.c
+++ b/mm/swap_cgroup.c
@@ -48,6 +48,9 @@ static int swap_cgroup_prepare(int type)
 		if (!page)
 			goto not_enough_page;
 		ctrl->map[idx] = page;
+
+		if (!(idx % SWAP_CLUSTER_MAX))
+			cond_resched();
 	}
 	return 0;
 not_enough_page: